Dialysis method and apparatus



D. H. BAILEY DIALYSIS METHOD AND APPARATUS June 24, 1941.

Filed July 13, 1938 I 5 Sheets-Sheet 1 dz'sATToR Ex/s June 24, 1941. D, BML Y v 2,247,143

DIALYSIS METHOD ANb APPARATUS Filed July 15, 1958 5 Sheets-Sheet 2 j; r '5 .7 v J3 L 4Z0 l-lll lll 20 41 g g Q76 INVENTOR.

- A745 ATTORNEYS June 24,1941. D. H. BAILEY 24 ,1

DIALYSIS METHOD ANDAPPARATUS Filed July 13, '1938 55!}6828-5119912 3 O O Q 0 Um ///f 1 M I a l/ 0 01/11 B .0 H M Z a alga vM June 24, 1941. pH. BAILEY $247,143 Y jnmmsrs rmuon AND APPARATUS Filed July 13,1958 S Sheets-Sheet 4 v I INVEN QR %ZISATTQRNEYS June 24, 1941. D. H. BAILEY '1 DIALYSIS METHOD AND APPARATUS 1 Filed July 13, 1938 5 Sheets-Sheet 5 INVE IQTOR.

%Z'S ATTORNEYS the. other. 1

pa a- June' 24, 194-1 U TED srA'rss PATENT FFICE Dana E. Bailey, Prescott, we... assimilto The Handler 00., Rochester, N. Y., a corporation of New York I Application July 1'3, weasel-ran No. 219,036

24 Claims. (01. 210-85) invention relates to a dialysis method and to apparatus for carrying out such method.

While my invention is concernedparticularly with the recovery of caustic hydroxides from impure solutions containing hemi-cellulose, oxya cellulose and other impuritiessuch as result from the so-called .steeping processor'mercerizin 9 pulp in the rayon industry; or the recovery of waste products resulting in the mercerization of yarns; or the purification and recovery of caustic hydroxides from the so-called black liquor from the digesters of pulp mills using the caustic methd of cooking: the method and apparatus offmy invention is by no means limited to such uses, and in general may be employed wherever the process of. dialysis may be advantageously used forthe recovery and purification of liquids or the concentration of solutions. I v i 4 For example, the method and apparatus of my invention may also be usedto separate impurities, such as salts, out of a colloid, such as glue, or,

in some cases, may be used to separate two cry v talloids where the diffusion characteristics of one crystalloid are appreciably slower than those of In the dialyzers of the prior art it has been customary to employ a plurality of cells or chambers, the adjacent walls of which are composed partly or wholly of specially prepared canvas or other "material to act as dialyzing membranes. The

membranes are nearly or usually 'wholly submerged between alternate layers of solution and solvent, the thickness'of the layers of the liquids or their extent in adirection perpendicular,

to the plane of the membranes beingusually about The liquids are usually two or three inches.

mentioned above. The rate of difiusion of the hydroxides through the membrane from the solution into the solvent, usually water, is dependent upon the concentration of solute hydroxide particles in the solution as compared with the con- ;centration of solute hydroxide particles in the solvent. When the concentration gradient of solute particles on opposite sides of the membrane is the same,'the condition is known as one of equilibrium. No further effective diffusion can take place although there may be, to a certain extent, an interchange of solute particles between of the membrane.

When, therefore, the rateof flow ofthe solvent and the solution past the interface of the memopposite sides brane is sluggish "the. dialyzation process must -.necessarily beslu"ggish,since the film of liquids at the interface of the membrane are substantially the only effective portions oflthe liquids and these portions rapidly approach a condition of equilibrium. Because only the two liquids at the interface of the membrane, at the most only thin layers or films of liquids on opposite sides of they membrane actively participate in the dialyzation process, the speed at which the-process may I be carried out is dependent upon therate'of pumped from one chamber to another in series;

and'due to the resistance to liquid ilow created in the dialyzing'unit the movement of the liquids in the chambers is relatively slug l h.- Moreover, the pump pressure which may be employed is relatively low. as it is necessary to keep the pressure pn the' membranes within reasonable limits toavoid membrane breakage. While the rate offlow of the liquid through the cells is slow,

this sluggishness is accentuated-at the interface change of the films or layers of the two liquids adjacent the interface of the membrane. As. has

been shown above, in the dialyz ersof the prior art, the rate of flow, through the cells, particu- "larly adjacent the membranes, is extremely slu g- I g'lsh. Any replacement of the layer of liquid'at the membrane interface by liquid further out in the cell stream is dependent upon motion of the solute 1 particles in accordance with the atomic'theo'ry or upon such agitation of the liquids as occurs as th% pass through the cells or chambers. The

- second of. these factors is ineffective. already pointed out above, the rate of flow through the cells is relativelyslow and, the liquids are relatively quiescent. The iirst is, of course, .insuficient to produce any appreciable interchange of 1 the liquids at the interface at the membranes.

, I have found that the rate of diffusion may be, materially increased by agitating the liquids or {creating a turbulence in the liquids on opposite brane is dependent, among other-factors,, upon the concentration gradient on opposite sides of the membrane. For example, consider the case of the recovery of caustic hydroxides from impure solutions resulting from thefsteeping process? sides of the membrane so that liquids which have been subjectedto the dialysis process are carried away from the interface of the membrane and replaced. More specifically, I have found that'the layer or of liquids closely adjacent the face of the membrane, as fast'as solute particles are d iflused through the membrane, should. be swept away and replaced by other. liquids, the case.

of the solvent by solvent of lower solute concentration, and in the case of the solution by solution of higher solute concentration. I have found that the liquids which have been subjected to diffusion may be swept oil the membrane and replaced most efiiciently and rapidly, tomaintain the concentration gradient of solute particles in the liquids on oppositesides of the membrane substantially at all times at a maximum, by dispersing the liquids over opposite sides of the membrane, preferably in a thin spray. The liquids, in the form of a thin film or layer, are then permitted to flow down the sides of the membrane by gravity. As the liquids flow down the membrane they are subjected todiffusion. The solvent, containing solute particles which have diffused through the membrane, is quickly swept from the face of the membrane by the oncoming solvent continuously directed onto the membrane and having a lower concentration of solute particles. The solution, containing solvent which has diffused through the membrane, is quickly swept from the face of the membrane 'by the oncoming solution continuously directed onto the membrane and having a higher concentration of solute particles. Thus, substantially at all times, the concentration gradient of solute particles in the liquids on opposite sides of the membrane is maintained in a maximum with the result that diffusion of the solute particles from the solution into the solvent is considerably more rapid than in the conventional dialyzation processes.

An object of my invention is to provide a dialyzing method and apparatus wherein diffusion through the membrane may be accomplished more rapidly than in the dialyzers of the prior art, thus permitting a decrease in siz of the dialyzing unit, a decrease in pumping costs, a

better and.cheaper product, and a general simplification of the'dialyzing system.

Another object of my invention is to provide a frame structure for a dialysis apparatus so constructed and arranged that the membranes may be so suspended as to permit stretching and shrinking of the membranesin accordance with temperature and moisture conditions.

Another object of my invention i to provide a dialyzing unit, the dialyzing membranes of which are subjected to a minimum of pressure to thereby lessen the likelihood of membrane breakage and permit the use of a thinner membrane enabling more rapid diffusion.

:Another object of .my invention is'the provision of a dialyzing apparatus in which the liquids ,(or either one of them separately) and the dialyzing membrane are moved with respect to I each other in a relatively rapid manner, the relative movement being accomplished and the dialyzation process being carried out without exerting any appreciable pressures on the membrane, other than the normal osmotic pressures 1 developed in the dialysis process.

Still another object of my invention is the provision of a dialyzing apparatus and method of dialysis wherein the solvent and the solution are maintained on opp site sides of the membrane in thin films or layers by the cohesion between the liquids and the membrane to thereby insure the active participation of all of both liquids in the dialysis process.

I A further object of my invention i the provision of a dialyzing apparatus and method of dialysis in which the ,solvent and the solution on opposite sides of the membrane, after being subjected to dialysis-are quickly swept oil the membrane and replaced, in the case of the solvent, by solvent of lower solute concentration, and in the case of the solution by solution of higher solute concentration, to thereby maintain the concentration gradient of solute particles on opposite sides of the membrane substantially at a maximum at all times.

More specifically it is an objectoi my inventlon to provide a dialyzing unit and method of dialysis in which the solution and the solvent are directed onto opposite sides of the membrane in a manner such that they flow by gravity down the sides of the membrane in a thin film or layer whereby substantially all the liquid flowing through the dialyzing unit actively participates in the dialyzing process; the solvent, containing solute particles diffused through the membrane, is quickly swept from the membrane and replaced by solvent of lower solute concentration; and the solution, diluted by solvent diffused through the membrane, is quickly swept off the membrane and replaced by solution of higher solute concentration, to thereby maintain the concentration gradient of solute particles in the liquids on opposite sides of the membrane substantially at a maximum at all times.

To these and other ends the invention resides in certain improvements and combinations of parts, all as will be hereinafter more fully described, the novel features being pointed out in Fig 1 is a front elevation of a single unit of my novel dialyzing apparatus;

Fig. 2 is an end elevation of the dialyzing unit Fig. 3 is a top plan View of the dialyzing unit;

Fig. 4 is a sectional view taken substantially on the line 4-4 of Fig. 3;

Fig. 5 is a sectional view taken substantially on the line 5--5 of Fig. 4;

Fig. 6 is a view taken substantially on the line 6-6 of Fig. 4; '7

Fig. 7 is a view taken on the line of Fig, 4;

Fig. 8 is a view showing the membrane in the somewhat bellied condition it may assume when the dialyzer is in operation;

Fig. 9 is a view showing one of the membrane carrying frames of the dialyzing unit; I

' Fig. 10 is a view showing an apparatus enabling adjustment of the pressure on the sprays;

Fig. 11 is a view showing a plurality of dialyzing units mounted in series;

Fig. 12 is a fragmentary view showing a different way of making the dialyzer frames and supporting the membranes;

Fig. 13 is a view taken on the line l3-I3 of Fig. 12;

Fig. 14 is a fragmentary perspective view showing two of the stationary frames in position;

Fig. 15 is a fragmentary perspective view showing the movable portions of the frames in position on the stationary portions;

Fig. 16 is a perspective view showing the bottom of one of theremovable parts of the frames;

Fig. 17 is a view similar to Fig. 4 showings. slightly different way of mounting "the membranes and a somewhat different form of collecting trough;

Fig. 18 is a view taken .on the line l8ll of Fig. 1'7;

' Fig. His 9. view taken on the line Ill-l9 of 2,247,145 I I 3 3s a) so that when the membranes ofthe .closed cellsbellyddwnward, asshowninFig. 8,.

I whichthe sprays may beimounted-in and cast. integrally with-the spacers;

Fig. 21 is a. sectiqnal viewgtaken onlthe 2l-,-2l.of Fig.'20; '1 V I Fig. 22 is-a bottom view-"of Fig-20;- r Fig. 23 is ajview showing a modified form of my dialyzing apparatus.

Y The same reference numerals-throughout the *several views indicate. the same of fluidwill be prevented. In of my invention instead of flooding the cellswith solvent andsolution, as :in the conventional type of .dialyzer, the liquids are onto the membranes through spray ripes ll. The apertures 45 in the spray pipes are relatively small and extend across the width of 7 Throughout the specification and claims I:will:;,1 the membranes betweenthe side arms of the the terms fsolveht, solution- =solute I in'the following mannerr'l'he solven "todenote the liquid, usually water, into which particles as, for example, caustic hydroxides are diffused through the membrane: from the lm-I. "pure caustic soda solution to enable recovery of the hydroxides, or the liquid into which the impurities are-diffused where a liquid is deleted pf impurities as, for example, when. salts or other impurities are to be removed-from a'colloidy-such a'sglue; the term solution to denote the liquid containing impurities and the substanceto be recovered or deleted of impurities, whether the desired substance is diffused through the mem- '-'brane and recovered in the solvent orwhether the impurities are difiusedthrough the membrane into the solvent and the desired substance left behind; andthe term solute to denote the particles which pass through the membrane from the solution into the solvent and whichparticles may be either the-material to be recovered, as in the recovery ofcaustichydroxides,

or the impurities, as in the separation of salts .fromglue.

- The dialyzing unit of my invention (Figs. 1, 2, Y

4 and 3) in which my novel method of dialysis is carried out compflsesa plurality of U-shaped frames 3|, the shape of each of which is shown in Fig. 9. The frames are formed with eyes 32 to receive tie-rods 33 by which the-frames 3| may be assembled and clamped-together with the openportions of the Us extendingdown ward. Prior to assembly there is interwoven around and between the frames a. membrane '34 which may becontinuous (Fig.4) -or in the form of separate U-shaped strips (Fig. 1'1). The membrane may be made of any suitable material such as specially prepared canvas, as

is well knownin the-art. ,AsshowninFigd there is thusformed a plurality of cells which are closed at the sides by the membrane and at the top by the frames. 1'

At the bottom each alternate cell as, forexample, cells 36, is open so as todischarge liquid flowing through these cells'--directly into a tank 3.! located below the dialyzer unit. The intermediate cells 38 are closed at the bottom by the "membrane 34. Alternate'frames, those forming the cells 38, at their lower ends areprovided with slots oropenings iusoasto'discharge liqfuidflowing down through these sidewardly from the dialyzingunit. Liquid from thecells 38 discharging h the openings 35 flows into aU-shaped trough ll "extending .on' three "sides of the'unit, As shown more-clearly in Fig.1

l, the tank 3 discharges'its contents into a 'sump'fl while the ll'idischargesj its 0011-;

tents into a sump.- While either set: of cells may be the solution cells, I prefer that. thesolu-v tion shall pass. downward through the closedcells. 38 and the solvent" the open 36. "The solution is, therefore, collected in the sum'p l3- and the solventin'the sump l2. The lower ends of the frames Meshaped (Fig. 6)

so as to at on the v-snap dupp r edges of sprayed onto .opposite sides of each of the mam frames so that the liquids are sprayed on the faces ofithe membranes uniform y across the I faces thereof in a. iine spray. Asindicated by the arrows (Fig. 4) each spray pipe has two sets of apertures (except thespray pipes. of the end cells) so that the liquids are directed onto .the membrane faces on both sides of each cell.

Ihepipes carrying the liquids enter preferably hand side and the solvent from theright hand side. The solution, by means of a'pump l8, taking its suction from the sump 43 and driven by a motor 49, is pumped through a pipe- 5| to a solution spray header 52. An overflow pipe 53, extending from the .header 52 back to the. sump' 43, is provided so. that the head of liquid on the sprays remains constant and is determined by the difierence in level between the spray pipe apertures and the liquid level in the inlet of the 5 overflow pipe 53. V A similar arrangement is provided for the solvent wherein a pump 5|, driven by the motor 49, draws solvent from the sump l2 discharging it.upward the pipeiifi to solvent spray tube header 51; An overflow pipe 58 serves to maintain the pressure on the solvent spray tubes constant.-

If desired a headermay be empioyedof atype e such that the head of liquid on the spray pipes may be varied (Fig. 10) In this construction the header 52 is provided with an upwardly extending leg 5|! and a flexible overflow tube. 55.

V the height of which maybe adjusted and which 45 discharges into the overflow pipe 53. By raising the flexible tube 55 the level of liquid in the upwardly extending leg 50 is raised so as to increase the head ofliquid on the spray apertures In operation, when solvent and solution are branes, as indicated by the arrows in Fig. 4, the

solvent and solution are directed onto opposite sides of the membrane faces at but a slight pres sure. I'he liquids flow down the'faces' of the membranes -in'a thin film orlayer, the liquids tending to beheld closely adjacent the 1118111. branes, as they flow downward by gravity, due to the cohesive forces between the liquids and the membrane; solute'particles exists between the solution and the solvent and as the liquids flow down' the membranes, diffusion 'of ="solute. particles takes place through the membranes into the solvent ,in accordance with well known osmotic laws.

As; previously mentioned, only a film 'of liquid on each face ,of the membrane-actively participates'inthe dialysis process and in the flooded'typ'e of cell, the concentration gradient of solute-particles at the interface of the membrane rapidly decreases andmay'even reach zero so that equilibrium is established. Norcsultimt diffusion of solute particles into the solvent, unden a condition of equilibrium-may take place. The

restoration of-a concentration gradient or the V A concentration gradient of v maintenance of such a gradient in a flooded type cell is dependent upon thesluggish flow of liquids through the cells, the slight agitation of the liquids which occurs by reason of this sluggish flow and the activity of the liquids in accordance with ionic theories. These factors are insufficient to prevent a condition approaching equilibrium at the interface as the solute particles near the center of the stream have to travel through an appreciable thickness of liquid to reach the face of the, membrane, and even those solute particles closely adjacent the interface fllm reach the face only by chance.

The positive and rapid interchange of liquid" closely adjacent the membrane face with liquid nearer the center of the cell stream is lacking in the conventional flooded cell dialyzer and, primarily for this reason, the process is ineflicient and sluggish.

In the dialyzer of my invention, as the solvent and solution flow down the membrane on opposite sides thereof in a thin film or layer, substantially the entire layer of liquid actively participates in the dialysis process. The concentration gradient is substantially continuously maintained at a maximum due to the fact that liquid whichhas been subjected to dialysis is swept off the membrane and replaced. As fast as difiusionof solvent through themembrane into the solution takes place, the solution diluted by solvent, by the continuous stream of solution flowing down the :membrane, is swept ofi the membrane and replaced by the oncoming solution of higher concentration. Similarly, the solvent flowing down the face of the membrane into which solute'particles from the solution have diffused, is quickly swept off the membrane into the tank 31 by the continuous stream of film flowing down the face of the membrane, and is replaced by the oncoming solvent of lower solute concentration. The concentration gradient is thus maintained substantially at all times at a maximum. 7

The dialyzer unit thus far described is particularly suited to the separation of salts or other impurities from colloids by batch operation where this process a batchof solution to be purified is introduced into the sump 43 and repeatedly passed through the dialyzer while solvent, usually water, is continuously fed to' the systemand discharged outside the system. Thus the concentration gradient is maintained at a maximum level as solvent containing impurities is continuously withdrawn from the system and replaced by pure water. Even where the concentration of solute particles in the solution is very low, a concentration gradient is maintained and diffusion of solute particles may take place through the membrane. It will be particularly noted that the liquids flow through the cells ,in parallel as distinguished from the usual flooded type of dialyzer where the cells operate in series.

One of the distinct advantages of the dialyzer and method of dialysis of my invention is that the membranes are not subjected to pump pressure. In the conventional type of dialyzer, a pump is used to pump the water through the cells inseriesrequiring an appreciablepressur'e, since -:the resistance toflow offered by the cells 'is considerable. The existence of thispressure necessitates a relatively thick, strong membrane. In addition, in the conventional type of flooded cell dialyzer, the membranes .are subjected to heavy osmotic pressures. Moreover, in most dialyzing processes the endosmose is prevalent. The cells containing the solution, therefore, tend to acquire an additional volume of liquid so that the membranes tend to belly out toward the solvent cells.

- endosmose can be retarded or reversed to a resultant exosmose. This is accomplished by heating the solution as it passes through the pipe 5| by means'of the heat exchanger 66, or by cooling the solvent by means of the heat exchanger 61, or if' desired, the solution may be heated and the solvent cooled simultaneously. The effect of heating the solution is probably to increase the activity of the solution in accordance with' ionic' theories to thereby increase the osmotic pressure of the solution and cause the solute particles to diffuse more rapidly through the membrane. The effect of cooling the solvent is probably to decrease the activity of the solvent and hence its osmotic pressure and the rate of diffusion through the membrane. By judicious use of a temperature gradient between the solution and the solvent, the normal endosmose may be materially lessened, or if desired, a resultant exosmose may be obtained. It is further possi- -ble, in the case of certain dialyzingproces'ses, that it may be desirable to maintain the solvent at a higher temperature than the solution to therethe colloid is the material to be recovered. In

by increase the normal resultant endosmose and decrease exosmose.

I have found in working with 10% sugar solutions that it was desirable, to prevent a resultant endosmose,-to use a logarithmic mean average temperature difference between the solution and the solvent of 8 to 15F. or an ingoing temperature difference between the sugar solution and the solvent in the neighborhood of 40 F. The temperature difference to be used, to prevent a resultant endosmose, will, of course, vary with the difference in osmotic pressures of the particular solution and solvent used.

In Fig. 11, I have shown a plurality of dialyzer units, substantially the same as that described above, arranged in series. The solvent enters through a pipe 68 and flows to a header 69, then through the dialyzer cells of the dialyzer 10 in parallel tothe sump II. The overflow from the header 69 is discharged through the pipe 12 to the sump H. From the sump H the solvent is unit 84 to the sump 86. From the sump 86 the solvent containing solute particles, is forced by means of a pump 81 to the point desired. The overflow from the header 83 is-returned to the sump 18 by means of a pipe 88. I

The solution enters the system through pipe 89 to header 9|. From the'header the solution flows by gravity through the dialyzing unit 84 to a sump 92. Overflow from the header 9| flows the header at is returned to the sump 02 by 'a P ped 'szby'a pump 9! the solution is pumped to a headerli thro gh a pip 91. the header 86 the solution flows by gravity through the dialyzing unit II to a sump I. .The overflow'from From the sump SB- thesolution is by a pump III to-a header I02 through 'alineili. Thesolution flows by gravity through the point desired-through a line Ifl. Overflow from the headerJfl is returned by a line I05 'the'dialyzing uniFIl-into a sump lfl fromlo 'whence it is pumped by means- 0f pump lli'to g It will be particularly, noted that the solution l flows through the dialyzer units in series in a Y C direction opposite to that of ;the movement-5of thesolvent. The purpose of-counter flowing the" elusive, a modified form of the frame structure I solutionand solvent is so'that thesolution of thus far described is shown. The frame struclowest concentration of solute particles will be.

subjected a; dialysis with the solvent of lowest concentration ofsolute particles, and conversely the solutionv of highest concentration of solute particles will be subjected to' dialysis with the through the dialyzer units in the same direction,'then, at the last dialyze'r unit, the concentration gradient of solute particles in 'the- V I I have also provided; as shown in' Fig. 11, a

'means whereby a portion of the solvent from each dialyzer unit maybe' recirculated through the same dialyzer malt from which it has I come. Such means comprises adjustable valves ,lls ahd one-way valves I09. By adjusting the .valve" It! a desired proportion.of.. solvent may pas through the pipe no basis tothepipe 5a and then through theedialyzer unit 10. Ina can be determined by the discoloration of the liquids. The solution may be observed bylifting the cover of the trough ll while the solvent inv thetank fl'maybe observed through thewindow 12!. The frames are then lmclampedand the j unaffected frames loosened from the frame to be cut out. The membrane is then slit. at the frame top on both sidesof the leak and the frame and cut-out membrane lifted out of the dialyzer unit. The torn portionwof the membranemay-then be replaced with new, the frames clamped together again, and the piping connected with the 'headera Membrane replacement can be easilveflected without a major shut down,

In the construction shown i rag 12 I516, in;

ture is made andthe-membranes arecarried so that membrane replacement in case of e; is'facilitated. "Hie dialyze'rframe of this modifloation comprises a plurality of fixed frames I2! solvent of highest concentration of solute parti- 5 cles, If the solutionand, the solvent moved solution would be substantially the'same as the 30 concentration of the solute particles in the sol- (Iig. 14) which are held'in spaced relation in 1 any suitable The fixed frames each eomprisesapair of vertically extending side arms I22 onlyone ofwhichis shown and ahorizontally extending top' member I23. Each of the side 7 arms I22 is wedge-shaped inhorizontalcrosssection with the narrow portion fof the wedge facing outward. The lower of the side arms the sump ,1; maybe circulated back. through 1 ing is provided withl adjustable valves III andv 'one-way-valves' 2, so that by adjusting the valves-I II the desired proportion of the solution may be recirculated through the dialyzer 8| or 11. r

'While in Fig. 1.1, inan effort to simplify the drawing, I-have not shown heat exchangers, it

- will be apparent that I-contemplate the use of heat exchangers as described above. The'heat for the solution. The lower ends of the removexchangers are preferably placed in lines 58, 89,

I4, I03, 82, and 51. "While I have-shown only three dialyzer units'in series, it is evident that more or less units maybeused.

One of the distinct'adv'antages' of the solvent the volume of watc required is material- 1y lessened, as-ifendosmose is. preventedno solvent passesinto'the solution; I am able to -use equal parts of solution and solvent, where: as in the-usual dialyzing apparatus about twice as much solvent as solution is used. This is partie luted.

' In the construction a: the dialyzeruhitthlls are V-shaped, assho wn .at 12!, to be received on av-shaped portion I25 of a supporting sill I21; I

The-topmembers I23 ofthe fixed'frames are wedge-shaped in vertical cross section with the taper of the wedge facing upward. The side arms and the top member of each of the fixed frames are preferablyformed integral andmay be either of wood or metal.

Interposed' between 'each of the fixed frames I2! lsva removable frame I28 (Fig. 15); The removable frames'each comprises a pair of 7 side arms I29 onlyone'of which is shown, and a j top'member -'I3I. The side arms I29 and the top similar manner a. portion of the soivent from 45 from the dialyzing unit. The side arms I29-are vs 6o of myinvention is that by maintainingateme perature gradient-between the solution and the 1 wedge-shaped in horizontal cross section, with the taper of the wedge facing inward to form 4 complementary surfaces with the wedge surfaces of the fixed side arms I22. Adjacent the top of each of the removable side arms I2; is an aperture I32 which is elongated ina vertical direction and which is adapted to receive a spray pipe able side arms I29 areV-shaped, as, shown at 1 I 33 (Fig. 16).:to be received onthe V-shaped top" of the sill I21. I The lower ends of the removable side arms I29 are alsoformed with apertures or slotsflfl throughwhich the solution when itv vreachm thebottom *of the membrane is discharged; The top members I31 of the removable I28 are wedge-shaped invertical cross section withthe taperof the wedge-extending downward to form complementary surfaces with the wedge-shaped portions of the topmembers' I23 of the fixed frames. There is thus formed a" substantially solid frame for the. di-

alyzer with alternate fixedand removable frames.

{ihe'membranesflii are U-shaped in cross sec; tioh and haveends I31, side walls I38, and closed iii. The membranes-are positioned in the dialyzing lmlt by'placing their endslfl ad-.

far described, in lease of membrane breakase, itment the tapered walls of the top members"! after locating the leak, the frames adjacent thei'ii of. -the flxed frames I2 audinterpesihgi-m In the event of membrane breakage after the leak has been located, the removable frame carrying the broken membrane is removed. The removable side arm I29 of the frame to be removed is moved upward, the elongated slot I32 permitting upward movement of the side arm with respect to the pipe until the V-shaped bot- ;tom of the side arm clears the V-shaped top of the sill, after which the side arm may be moved sidewardly away from the dialyzing unit to be suspended by the spray pipe on the upper margin of the slot I 32. After the removable side arms on both sides of the dialyzing unit have been. displaced, the top member I3I may be pulled upward to release the membrane. Thetorn membrane is then quickly removed, a new one inserted in position, and the removable top member I2I placed in position for retaining the membrane in suspended condition. The removable side arms may then be replaced. The entire operation may .be accomplished without disturbing any piping,

and in fact by cutting off the supply of solution to the afiected cell replacement of a broken membrane may be accomplished without a shut-down.

In Figs. 17 to 19, inclusive, I have shown another way in which the dialyzing membranes may be mounted. In this construction the membranes I H are U-shaped as in the modification just described, and held in fixed position by means of U-shaped frames I42 similar to the frames shown in Fig. 9. Tie rods, similar to those shown in Fig. 2, may be used to clamp the frames together. There is thus formed a series of alternate open and closed cells inwhich.

themembranes are separate from each other. When the tie-rods are unloosened to permit separation of the frames, removal of a broken membrane and replacement by a new membrane may be quickly efiected. In this'construction at the lower end of theunit there is provided The' solvent fiows by gravity down the sides of the membranes in a thin film .or layer, falls into a tank I43 having a discharge pipe I44.

the trough I43 and is carried away by the pipe I44. The lower ends of the solution cells are closed and adjacent the bottom of each of the solution cells there is provided a trough-like pipe I46 intowhich the solution flows. The solution is carried away by a common discharge pipe I41, into which all of the troughs empty. The advantage of using trough-like pipes in the solution cells is to avoid the pronounced bellying of the membrane, such as is likely to -occur as suggested in Fig. 8.

- I In Fig. 23 I have shown a modification of my invention wherein the membranes I52 extend at an angle to the vertical and are supported at the sides by spacers or frame members I54.

In this construction the 'fluid passages and spray nozzles may be formed integrally with the frame members, as shown at I56. In this form of the invention, the center of the dialyzing'membranes is the low point, and the solution and solvent flow on opposite sides of the membranes from the frames downwardly along the membranes toward the center. At the center troughs are provided for the separate collection'of the solution and the solvent. The solvent troughs are indicated by the numeral I51 and the solution troughs by the numeral I56. As shown by the arrows'the solution or solvent will fiow along the upper sides of the membranes by gravity and into the troughs. The solution or'solvent will flow along .the under sides of the membranes by gravity and be held against the membranes by the cohesion between the. membranes and the solution or solvent. When the solution orsolvent reaches the centers or low points of the membranes, it will drop into oneof the troughs I56 or I51. As the solution and solvent flow down the opposite sides of the membrane, diffusion takes place in the manner described above. It will be understood that heat exchangers may be used in the supply pipes of this form of dialyzer to maintain a temperature,

gradient between the solution and the solvent.

While I have shown and described various forms of dialyzer apparatus andhave described the preferred method of car y ng out the dialyzing process of my invention, it is apparent that various other arrangements and constructions will readily suggest themselves to those skilled in the art, within the scope ofmy invention' as set forth inthe appended claims.

I claim: v

1. A dialyzing apparatus comprising, in combination, a multiplicity of frames supported substantially vertically, membranes carried'by said frames, spray means for distributing a substantially continuous, even film of'solvent on one side of each of the membranes, spray-means for distributing a substantially continuous, even film of solution on the other side of 'each'of the membranes, means for maintaining the spray pressures of the liquids on opposite sides of the membranes substantially the same, and means adjacent the bottoms of the membranes for separately discharging the solution'and solvent, said last mentioned means being of such discharge capacity that the spaces between the membranes will not be flooded.

2. A dialyzing apparatus comprising, in combination, a multiplicity of frames supported sub.- stantially vertically, membranes carried by said frames, means for distributing a substantially continuous thin film .of solvent on oneside of each of the membranes, meansfor distributing a substantially continuous thin film of solution on the other side of each of the membranes,

means for maintaining one 'of said liduids at'a higher temperature than the other, and means adjacent the bottoms of the membranes for separately. discharging the solution and solvent, said last mentioned means being of such dis charge capacity that the spaces between the membranes will not be flooded.

3. A dialyzing apparatuscomprising the com-' bination of a plurality of frames, membranes for separating the solvent from the .solution carried by said frames at an inclination to the .branes.

' horizontal, said plurality of frames-constituting, a unit, a plurality. 91 such dialyzing units, means for passing-the solvent through each of said units in parallel and through the plurality of units in series in one direction, and

- means for passing, the solution through each of 4. A dialyzing apparatus comprisingin com-- ination, a multiplicity of frames supported sub-'- and means adjacent the-bottoms of said membranes for separately collecting and discharging said solvent at least as fast as it is supplied by said spray means so that said surfacesof said membranes remain substantially unflooded.

' s antially vertically, membranes carried by said frames, means including a spray for distributing a substantially continuous, even .film of solvent V on one sideof each of said membranes, means for'distributing a substantially continuous, even film of solution on the other side of each of said membranes, means for varyin 'the spray pressures of the liquids on opposite sides of the membranes, and means for separately collecting the' solve'nt and-Tth'e solution. 1,

5. A dialyzing apparatus comprising, in combi- 1 nation, a plurality of membranes, means for sup- V porting said membranesin spaced relationship,

: said membranes being inclined to the vertieal and all being substantially parallel to each other,

- means for directing a stream of solvent onto one 1 side of each of the membranes, means for .direct--. ing a solution to'the other side of each of said -membranes, and means for collecting the solvent plied by said spray means so that said sprayed "and solution separately at least as'fast as theyvent flooding thereof.

' are directed onto said membrane sides to pre- T 6. A dialyzing apparatus comprising in 00meach of the framesbeing'supported vertically,- membran'es carried by said frames, said mem branes separating a-solution from a solvent, a

Vs-shaped sill engaging the lower ends voi the frames, the frames having ends cooperating with bination, amultiplicity of ,U -shaped'frames 9. A dialyzing apparatus including, in combination, a multiplicity of frames, membranes carried by said frames and dividing said apparatus into a series of chambers, said membranes having a substantial surface on each extending substantially unobstructedly at an inclination to the horizontal, means includingsprays irrcertain of said chambers adjacent the tops of said membranes for directing a-substantially continuous stream of liquid solution onto said surface of each of said membranes so that it flows down the surface of said membrane in a thin, sheetlike film, said film'being held on said membrane primarily by the cohesive forces between said. membrane and said solution, means for directing a solvent onto the other side of'each of said membranes, and means adjacent the bottoms of said membranes for separately collecting and discharging said solvent at least as fast as it is supsurfaces, of said membranes remain substantially unflooded. 4

10. A dialyzing apparatus'comprising, in combination, a multiplicity-of UJ-shaped framesreach of the frames being supported vertically with the open portions extending downward, vU--shaped membranescarried by said frafneswith the open portions of said membranes extending upward, said membranes separating a solution from a 'solvent, and a V-shaped'sill engaging the lower ends of the frames, the frameshaving ends shaped to cooperate'wlthsaid" sill and clamping the membranes therebetween to prevent leakage.

'11. In a-vdialyzing apparatus, in combination,-

a plurality of dialyzingunits each comprising a plurality of inclined frames, membranes carried 1 by said frames for separating a solvent from a solution, said membranes dividing th unit into a series of chambers, means for directing the solsaid sill and clamping themembranes therebetween to prevent leakage.

7'. A dialyzing apparatus comprising a' plurality of alternate fixed and removable frames, said iixed frames having wedge-shaped top" members and said removable frames havingcomplementary separately removable wedge-shaped top members and separately removable side'members,

membranes carried by'the wedge-shaped portions of said top members in a suspended condition,

vent and the solution onto the opposite sides of each of the membranes of each unit 'so that the,

liquids flow by gravity over the faces of the membranes, said chambers having outlets for discharging said liquids at least as fast as they are 1 supplied thereto so that the chambersare un-' flooded, and meansfor circulating said liquids separately throughthe series of units in direc tions countercurrent to each other.

12. In a dialyzingapparatus in combination a "plurality of frames, membranes carried by said said removable top members and side members" being constructed and arranged, upon' removal,

to free the adjacent membrane individually for removal and replacement. V r

8. "dialyzing apparatus including, in combi-f nation, a multiplicity of frames, membranes .car- 3 ried by said; frames and ,dividing said apparatus 2 into. a series ofchambers, said membranes having a substantial sm'face on eachextendin'g substantially unobstructedly at an inclina branes for directing a substantially continuous 1 stream of liquid solvent onto said surface of each than to the.

horizontal, "means including sprays in certain of said chambers adjacent the tops of saidmemofsaid-membranesso that it flows down th surmembrane face of said membrane in rms, sheet-like iihn, I said filmbeing' held on said membrane primarilyby the. cohesive forces between said framesfor separating a solvent from a solution; said plurality of frames constituting a 'dialyzing.

-,unit and the membranes-dividing the unit into a seriesof chambers, a plurality of such dialyzing unit's, means located adjacent the tops of 'each of themembranes for supplying-a solution and a solvent ontoopposlte sidesof each of themem-I- branes, -'means located adjacent the bottom of each 'of said units jfor'separately collecting the ,solution and the solvent, saidcollectln'g; means cooperating to'malntain-thechambers in an .un-.' flooded condition so that the liquids flow down' the membranes by. gravity and in thin liquid strata;-- means for separately conveying the liq- ,uidsfromthe bottom of one unit to the top of .anothe g said last mentioned means being arranged sothat ,the liquids flow throughthe' pluand said solvent; means for directing a solution onto the other-side of each of said membranes,-

rality of units in directions counter-current to each other.

13. A method of dialysis adapted for continuous operation which includes the steps-of separating a solvent from a solution by a stationary membrane inclined to the horizontal, continuously supplying solvent to one side of the mem-' brane, continuously supplying solution to the other side of the membrane, distributing the solution over the membrane in a thin liquid stratum on one side of which is the membrane and the other side of which is free and unsupported,

said flow being maintained with both sides of the membran substantially free of liquid pressures and unflooded, and separately collecting at least one of said liquids after flowing over said membrane.

18. A method of dialysis adapted for continu- 'ous operation which includes the steps of separating a liquid solvent from a liquid solution by a membrane supported ina stationary position at an angle to the horizontal, directing one of said liquids onto one side of the membrane and directing the other of said liquids onto the other side of the membrane, causing at least one of said liquids to flow down an unfiooded side of the membrane in a thin film substantially entirely by gravity and restricted substantially only by contact with the membrane, while the membrane on both sides thereof is maintained substantially free of liquid pressures, and separately collecting at least one of said liquids alter fiow over said membrane.

19. A method of dialysis adapted for continuous operation which includes the steps of sepavent onto the other side of the membrane, permitting the solution and solvent liquids to flow substantially unrestrictedly down the opposite sides of and in contact with the membrane, en-

tirely by gravity, while the membrane considered as a whole is maintained substantially free of any liquid pressures and unflooded, and separately collecting at least one of said liquids.

15. A method of dialysis which comprises separating a liquid solvent from a liquid solution by a membrane inclined to the horizontal, directing the solution onto the membrane, permitting the solution to flow and fall entirely by gravity over the membrane in a film, directing the solvent onto the opposite side of the membrane, permitting the solvent to flow and fall entirely by gravity over said other side of the membrane in a film, withdrawing said liquids after flowing over said membrane so as to maintain the same unflooded and separately collecting at least one of said liquids.

16. A method of dialysis which includes the steps of circulating a solution and a 4 solvent through a series of dialyzing units each comprising a plurality of membranes inclined to the horizontal, one of said liquids being introduced at the first of said units and; progressing to the last of said units and the other of said liquids being introduced at the last of said units and progressing to the first of said units, so that said liquids flow through said units, as a whole, separately and in countercurrent to each other, distributing one of said liquids over the upper portions of one side of each of said membranes, and the other liquid over the upper portion of the other side of each of said membranes, to cause said liquids to flow downwardly thereover by gravity in the same direction in thin films supported only by the cohesive forces between said liquids and said membrane, withdrawing said as they are distributed thereover to prevent flooding of said membrane sides and separately collecting at least one of said liquids. 4

1'7. A method of dialysis which comprises separating a solvent from a solution by an inclined membrane, discharging said liquids onto upper portions of opposite sides of said membrane, respectively, and causing the same to flow downwardly in a thin film substantially unrestrictedly over the major portion of the surface of the membrane and substantially entirely by gravity,

rating a liquid solvent from a liquid solution by a stationary membrane supported at an angle to the horizontal, continuously supplying solvent to one side of the membrane, continuously supplying solution to the other side of the membrane, directing at least one of the liquids over one side of the membrane in a film and in such volume that most of the liquid flowing over the membrane is held thereon primarily by the cohesive forces between the membrane and the liquid, causing the other of said liquids to flow over the other face of said "membrane, drawing off the liquid of said film after flow over said membrane to prevent flooding said membrane side and to I maintain continuous replacement of treated liquid by liquid of different concentration by a sweeping action of oncoming liquid over a subopposite sides of each of the membranes, one of liquids after flow over each membrane as fast said liquids entering the dialyzing system at the first unit and progressing to the last unit and the other of said liquids entering the dialyzing system at the last unit and progressing to the first unit, the flow of the liquids through the system as a whole being countercurrent to each other, directing said liquids onto opposite sides of each of said-membranes,-respectively, for flow downwardly thereover by gravity in the same direction in thin films maintained by the cohesive forces between said liquids and membrane, and collecting said liquids as fast as they are discharged from-said membranes to maintain the same substantially unflooded.

21. A dialyzing apparatus comprising a plurality of alternately fixed and removable frames, said fixed ,frames having wedge-shaped top members and said removable frames having complementary, separately removable, wedgeshaped top members and removable side members, membranes carried by said wedge-shaped portions of said top members in suspended position in said apparatus, said removable top members and side members being constructed and arranged, upon removal, to free the adjacent memw 2,24%5143- branes, individually, for removal and replacement. 22. A dialyzing apparatus comprising a dialyning membrane arranged at an inclination to the horizontal and having on at least one side thereof a substantially unobstructed surface, liquid conducting means having outlet means for disj 'tributing one of said liquids over the upper portlon of said membrane surface in a volume sufflcient to produce a thin film of said liquid flowing by gravity over and supported only by saidsurface and having substantially the thickness produced by the cohesive forces between-said liquid and said membrane, discharge means for withdrawing the liquid of said film as fast as it flows over said membrane surface to prevent flooding thereof, conducting means for supplying the other of said liquids for flow over the opposite side of said membrane, and a conductor for separately collecting at least one of said liquids after flow over said membrane.

23. A dialyzing apparatus comprising a dialyzing membrane arranged at an inclination to the horizontal, liquid conducting means having outlet means for distributing a liquid solution 5 against the upper porfion of one side of said membrane in a volume sumcient to produce a thin film flowing by gravity over and supported only by said membrane, said film having substantially the thickness produced by the cohesive forces between said solution and saidmembrane,

conducting means for supplying a liquid solvent to the opposite side of said membrane, and a conductor for collecting one of said liquids after 7 contact with said membrane.

'24. A dialyzing apparatus including, in combination, a multiplicity of dialyzing membranes each having the opposite sides thereof-extending substantially unobstructedly at an inclination to the horizontal, liquid conducting means provided with discharge openings constructed and arranged for directing a liquid solvent and a liquid solution onto upper portions of said opposite sides of said membranes, respectively in volumes sufficient to produce a gravity flow over each of said sides of a film supported only by said side.

- I or cqnnncnou."

v June 214., 1914.1. 1mm g.

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